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Recent seismic design approaches developed under the umbrella of performance-based earthquake engineering (PBEE) pursue pre-defined performance objectives in terms of structural response, economic losses, or casualties. The earlier PBEE methods were mainly concerned with the deterministic evaluation of performance at a single ground motion intensity level. This premise, however, provides little insight into the long-term risk-based performance of a structure, and limits the ability to make informed design decisions. Given the inherent sources of uncertainty in all aspects of seismic design, probability theory needs to be employed to enable reliable design solutions. However, applying a risk-oriented design approach is not currently feasible for most practitioners, making it essential to understand how the current deterministic applications of these intensity-based PBEE approaches perform in terms of risk. Specifically, the aim is to investigate the capability of the direct displacement-based design (DDBD) method in producing reliable, risk-consistent designs. A probabilistic PBEE assessment framework is applied as the benchmark to determine the risk of exceeding performance objectives for multiple DDBD-based reinforced-concrete-wall and dual reinforced-concrete-wall/steel-frame buildings located at three different sites. The significant variation in the achieved risk estimates related to the limit states of damage limitation, life safety and global collapse for the buildings considered, questions the ability of DDBD—or any other intensity-based design method that does not account for uncertainty—to offer risk consistency. [ABSTRACT FROM AUTHOR]

We present a seismic source characterization model for the probabilistic seismic hazard assessment (PSHA) of the Isfahan urban area, Iran. We compiled the required datasets including the earthquake catalogue and the geological and seismotectonic structure and faults systems within the study region to delineate and characterize seismic source models. We identified 7 relatively large zones that bound each region with similar seismotectonic characteristics and catalogue completeness periods. These regions were used for calculating the b-value of the Gutenberg–Richter magnitude recurrence relationship and for estimating the maximum magnitude value within each region. The earthquake recurrence parameters were then used to build a spatially varying distributed earthquake rate model using a smoothed kernel. Additionally, based on a fault database developed in this study and on a local expert's opinion supported by tenable constraints about their slip velocity, a fault-based model is also created. We further performed sets of sensitivity analyses to find stable estimates of the ground motion intensity and to define alternative branches for both the seismogenic source and ground motion prediction models. Site amplification is considered based on a Vs30 map for Isfahan compiled within this study. The alternative source and ground motion prediction models considered in the logic tree are then implemented in the software OpenQuake to generate hazard maps and uniform hazard spectra for return periods of interest. Finally, we provide a detailed comparison of these PSHA outcomes with both those presented in the 2014 Earthquake Model of Middle East (EMME14) and with the national seismic design spectrum to further discuss the discrepancies between hazard estimates from site-specific and regional PSHA studies. [ABSTRACT FROM AUTHOR]

This study applies the latest probabilistic performance-based earthquake engineering tools in terms of nonlinear dynamic analyses in tandem with hazard-consistent record selection to assess the risk of collapse of RC tall buildings in the Istanbul metropolitan area and to quantify their seismic safety margin with respect to acceptable risk levels. Statistically representative archetype buildings selected from an extensive inventory form the basis for this assessment study. Accordingly, we chose five hypothetical building sites in Istanbul where tall buildings are densely populated to estimate the risk of collapse for 5 × 5 = 25 building-and-site specific cases. The results showed an average 10% probability of collapse under the ground-motion intensities with 2% probability of exceedance in 50 years. The mean annual rates of collapse range between 0.1 × 10–4 and 6.1 × 10–4 with an average of 1.7 × 10–4, which remains below the tolerable risk threshold value of 2.0 × 10–4 envisioned by the FEMA's Building Seismic Safety Council. However, 36% of the analyzed cases yielded collapse rates higher than this tolerable risk. Among the considered cases, the core walls and frame building was identified as the best design choice from a collapse safety point of view while the tunnel form archetype raised concern by exhibiting substantially higher collapse risk compared to other archetypes. [ABSTRACT FROM AUTHOR]

Since the early twenty-first century, tall building construction has gained significant momentum in the urban cities of Turkey as a result of the population and economic growth. Accruing more than 1500 buildings by year 2015, the majority of the country's exposure now clusters across the seismically active landscape of the Istanbul metropolitan area. As such, the underlying earthquake risk calls for the investigation of the seismic performance of these structures. While hazard studies for Istanbul are available, the literature is still devoid of studies related to the seismic risk assessment of tall buildings located there. As an attempt to fill this gap, this paper focuses on the characterization and quantification of the existing exposure to allow risk assessment both at single building and portfolio levels. To this end, an extensive tall building inventory containing the structural drawings of 94 buildings is compiled and thoroughly examined to make a projection of the design practice. After establishing statistically representative archetypes, we quantified their dynamic response to 1999 Düzce and Kocaeli earthquake ground motions. We notice a maximum difference of 100% in the maximum interstory drift ratios (equaling a 2% increase in absolute value) between two different tall building archetypes. Moreover, the analysis results indicate that the incident angle of the applied ground-motion can be a discriminant factor between structural collapse and survival. The outcome of this study puts forward a robust basis for prospective structural analyses, collapse risk assessment as well as loss estimation analyses of tall buildings in Istanbul. [ABSTRACT FROM AUTHOR]

Regional, multi-country seismic hazard models provide a comparison basis for national seismic hazard models that are generally used to underpin the seismic design prescriptions of national building codes. Our study presents an attempt to formalize a framework for performing such a comparison. This comparison consists of sequential steps for identifying and understanding similarities of the key elements informing the seismic hazard models and the code design ground motions in addition to their numerical comparison. The challenge may arise, on one hand, from the lack of transparency of some national seismic codes and, on the other hand, from the intrinsic difficulties in comparing seismic hazard models. In this study, as an example we compare the seismic design spectrum of the Iranian national design code with the uniform hazard spectra from the recent, fully-harmonized, cross-borders Earthquake Hazard Model for the Middle East region (EMME). This comparison focuses on the two 10% in 50-year exceedance probability maps for PGA and on the pairs of design spectra for four cities with different seismicity levels. While, in general, the two reference maps for PGA on rock seem similar, the comparison of the uniform hazard spectra and design spectra for the four selected cities for different soil conditions show large differences. We offer some plausible causes for these differences as well as generic recommendations for overcoming them. [ABSTRACT FROM AUTHOR]

Average spectral acceleration, AvgSA, is defined as the geometric mean of spectral acceleration values over a range of periods and it is a ground motion intensity measure used for structural response prediction. One of its advantages stands on the assumption that its distribution is computable from the available GMPEs for spectral acceleration, GMPE- SA, (called here indirect method) without the need for deriving new specific GMPEs for AvgSA, GMPE- AvgSA, (called here direct method). To what extent this assumption is valid, however, has never been verified. As such, we derived an empirical GMPE- AvgSA based on RESORCE ground motion dataset and we compared its predicted values with those from a GMPE- SA via the indirect approach. As expected, the results show that the indirect approach yields median AvgSA estimates that are identical to those of the direct approach. However, the estimates of AvgSA variance of the two methods are identical only if both the GMPE- SA and their empirical correlation coefficients among different SA ordinates are derived from the same record dataset. [ABSTRACT FROM AUTHOR]

The adequate seismic performance of transportation infrastructures is important for the functioning of the economy and society. This paper focuses on the seismic assessment and analysis of one of the most important components of these infrastructures, the bridges. In this field, nonlinear static procedures (NSPs) have gained significant attention, resulting in different proposals to improve the accuracy of the procedures while keeping their simplicity. The main goal of this study is focused on the evaluation of the applicability of NSPs for irregular reinforced concrete viaducts. A comparative approach is pursued by resorting to (1) the analyses of the performance of three well-known NSPs (N2 method, modal pushover analysis and adaptive capacity spectrum method) and (2) the extension of the scope of previous studies in this field to a more recent method, the extended N2. As such, a set of bridges with different levels of irregularity, configurations and lengths is investigated. The accuracy of different NSPs is evaluated by comparing the results of NSPs with the ones obtained by means of nonlinear dynamic analyses. The comparison of results confirms the acceptable performance of the multi-modal NSPs and highlights the effectiveness of extended N2 method with respect to its simplicity. [ABSTRACT FROM PUBLISHER]

The influence of the effects of the degradation of materials on the seismic fragility of Cultural Heritage buildings in Granada (Spain) is investigated. The degradation of the material, which mainly happens at the lower levels of the façades, is obtained by using 3D photogrammetry data. Fragility curves for three cultural heritage constructions in Granada are calculated by using FE nonlinear dynamic analyses for both non-deteriorated and deteriorated geometries. The Finite Elements (FE) models, based on the macro-modelling technique, are subjected to ground motions for the city of Granada, which were selected by considering Probabilistic Seismic Hazard Analysis (PSHA) methodology with their probability of occurrence. The response of each model is analyzed for different seismic Intensity Measure (IM) levels, which, in this study, correspond to average pseudo-acceleration. The procedure is applied to three monuments in Granada that were built with two different constructions materials: calcarenite and rammed earth. The damage mechanisms considered are roof displacement or maximum compressive principal stress, depending on each case. The results show that the restoration works that have been carried out has prevented structural failures in the rammed earth construction studied, and that, during future seismic events, special attention must be paid to the level of compressive strengh reached in the Santa Pudia calcarenite used at the San Jerónimo monastery. [ABSTRACT FROM AUTHOR]

This paper focuses on the exposure and fragility/vulnerability of the residential, mixed residential/commercial, and public building stock of the city of Isfahan, in Central Iran, and constitutes the first part of a seismic risk assessment study for that city. To determine the assets at risk, we first summarize the details of the building stock and population from the available georeferenced 2011 Census data. From this dataset and from a local survey of the city, we categorize the building taxonomy in 27 construction classes characterized by age, height, and material/lateral-load-resisting system. A building exposure model is then assembled by first dividing Isfahan in city blocks and then by assigning the appropriate statistical properties to the buildings, such as construction class, built area, and replacement cost. The population of each city block is also estimated and accounted for. To assess the fragility and vulnerability to earthquake ground motion, for each building class we performed nonlinear dynamic analysis of multiple equivalent single-degree-of-freedom systems. This process generated a set of class- and region-specific fragility and vulnerability functions that considered both record-to-record and building-to-building response variability. In the companion paper we used the exposure model and the fragility and vulnerability curves generated for all these asset classes to probabilistically assess the seismic risk of Isfahan. [ABSTRACT FROM AUTHOR]

The second part of a seismic risk assessment study for the Iranian city of Isfahan is presented, focusing on the description of the hazard, the risk analysis, and the discussion of the results. This study utilizes the building exposure model, the fragility and the vulnerability curves illustrated in the companion paper. The earthquake occurrence source model adopted is based on the EMME14 hazard study. The site effects accounting for the soil nonlinear behavior are modeled by means of a Vs30 map derived from the topographical slope. The validity of this map is tested based on the local surface geology and geotechnical reports. The probabilistic seismic hazard maps for different return periods that account for site effects are generated and compared with the design spectra mandated by the Iranian national seismic design code. In addition, direct seismic monetary and human losses are estimated for two earthquake scenarios and also for 100- and 475-year return periods. We show loss maps and loss curves, offering insights on the most vulnerable building classes and the spatial distribution of the estimated losses. The results provide a basis for pre- and post-disaster emergency planning, for global and local urban planning, as well as for conceiving adequate risk mitigation strategies including devising fair earthquake insurance policies. This study may also serve as a blueprint for carrying out similar work in other urban areas of the Middle East. [ABSTRACT FROM AUTHOR]

Automated Multi-Depth Shuttle Warehouses (AMSWs) are compact storage systems that provide a large surface occupation and therefore maximum storage density. AMSWs represent the future of storage technology, providing substantial savings in terms of cost, space, and energy with respect to traditional warehouses. Currently, designers refer to the standard building codes for the seismic design of AMSWs. Since structural characteristics of AMSWs are considerably different from the steel structures of typical buildings, this current approach used by designers is questionable in terms of safety and efficiency. In this article, the behavior of 5 AMSW structures has been studied performing 150 time-history analyses by direct integration including P-Delta effects. Demand/capacity ratios calculated for each element showed the dominance of the brittle failure mechanism in AMSWs subjected to low-to-moderate seismic actions. These mechanisms mainly took place in upright columns and their base connections prior to the activation of ductile energy dissipation mechanisms of the structure. Based on the results, further improvements have been recommended for the future design provisions, which may lead to a safer seismic design of AMSWs. [ABSTRACT FROM AUTHOR]

A risk-consistent approach is proposed for the evaluation of behaviour factors that are compatible with Eurocode 8, using nonlinear static and dynamic analysis. It comprises seven discrete steps, involving hazard assessment and record selection at multiple sites, designing and modelling multiple archetype buildings and assessing their performance vis-à-vis target safety objectives. In all cases, uncertainty is incorporated and propagated to the final results whereby a flexible verification procedure is offered to account for the confidence of the investigator on the data available. An example application is offered on steel concentrically braced frames, highlighting the need for selecting appropriate performance targets for Europe. The overall added value goes beyond the current state of art, offering a consistent risk basis for the seismic design of different systems that is compatible with current uniform hazard design spectra and can benefit from future risk-targeted hazard maps. • A risk-consistent approach is proposed for deriving EN1998 compatible behaviour factors. • Hazard assessment, record selection and incorporation of uncertainty are important aspects of the approach. • Setting appropriate performance targets is required to achieve consistency with current EN1998 implied safety. • An example is shown for steel concentrically braced frames. [ABSTRACT FROM AUTHOR]